For self-managed instances using the experimental [external pipeline validation service](https://docs.gitlab.com/ee/administration/external_pipeline_validation.html), the range of error codes GitLab accepts will be reduced. Currently, pipelines are invalidated when the validation service returns a response code from `400` to `499`. In GitLab 14.0 and later, pipelines will be invalidated for the `406:Not Accepted` response code only.